Personally, I think people should do what's right for them. For some, financing makes sense. For example we bought at Grand Californian when there were strong enough incentives that it made sense to buy, even though we had to finance.
But at the time, we also only had four car payments left on a car that should have lasted us another good 10 years. So, we were planning on throwing the money that we were spending on our car payment as extra to pay it off faster. The problem was a couple months later a drunk driver decided to hit it while it is parked on the street by our house. Well, that totaled the car and now we have a car payment.
That being said, we have looked at it and for us it still makes sense to keep our
DVC membership, even with the financing based on the interest rate, dollar amount, etc. we still throw extra money at it when we can, but not as much as we were going to be doing.
Will we save money in the long run? Probably not, because if we didn't have it we would stay at the value resorts and quite often at a discount of some sort. But we will be able to stay in nicer accommodations and it will cost us just a bit more than staying in the values in the long run.
Bottom line is I don't compare cost of points from one year to another year, I compare the cost of points (including financing) to the cost of staying elsewhere.
Then there are the intangible benefits, such as it feeling more like a home away from home than a hotel room, the little extras you get by being a member around the parks, on the cruises, etc. In other words you feel like you get a little bit of special treatment being a member. Some of these things are difficult to put a price on.
Add in the fact that you know you will be taking a vacation every year and really that is why financing may make sense (maybe not on paper, but by good old gut feeling) for some people.
And yes, we made sure that we could easily afford the monthly payments, even with the car payments before purchasing because you never know what might happen.
The PP posted while I was writing this. The situation he describes is us. We would spend $3,000-$5,000 or so a year on the hotel room portion of our vacations to Disney World and were doing them yearly. It works out where about 5 years worth of these vacations will pay for the DVC membership. Things have happened that has slowed our ability to get that payed off in the 5 years we were planning on, the car, the economy, etc. So it will probably take us a little longer, but still not bad and then we won't have to pay for a room anymore. Just our yearly dues. So again, financing made sense, because we couldn't do the yearly trips and save the money to pay cash for DVC. Some might say skip the yearly trips for a few years, but it is truly one of the chances I get to recharge each year and my work has a use it or loose it policy with vacation. And since I get three weeks a year, I definitely need to use it somewhere. We usually do about 10 days at Disney World after about a week with my family for Christmas and then a few others throughout the year. By doing this at Christmas time, I get a couple of extra days as well. Usually this equates to about two weeks of my vacation time, unless the holidays land strange and they give us the week between Christmas and New Years off paid, which sometimes happens as well. So, as you can see I can get a fair amount of time off, leaving the idea of skipping vacations for a few years a very unappealing one.
I did the opposite.
But, we went the other route, didn't know about DVC until last year, and we bought a resale outright. 
